Refining of heater oil



United States Patent REFINING OF HEATER 01L Jack H. Krause, Hammond, Ind., assignmto Standard Oil Company, Chicago, Ill., a corporation of Indiana Application July 18, 1952, Serial No. 299,687

5 Claims. (Cl. 196-30) This invention relates to a process for refining distillates boiling in the heavier-than-gasoline range. More particularly, it relates to the production of a sweet, color stable distillate which is suitable for use as a burning oil, diesel oil, or jet fuel. Still more particularly, the invention is directed to the refining of a heavier-thamgasoline distillate which contains mercaptans and substantial amounts of phenols.

A very large demand eXists for petroleum distillates which boil in the heavier-than-gasoline range, i. e., within the range between about 300 and 650 F. These distillates have a tremendous demand for use in domestic heating installations; oils for this purpose are generally known as burning oils, furnace oils, or heater .oils. Still another large demand for these distillates is for illumination purposes; oils for this use are generally called kerosene or burning oil. Another large use for oils of this type is as fuels for diesel engines. A rapidly growing use for oils of this type is in the reaction propulsion engine, i. e., jet propulsion; oils for this use are generally called jet fuels or IP-fuels. In general straight run (virgin) distillates are preferred for these uses, but cracked distillates are also often used, particularly for domestic heating purposes. Consumer demand 'hasforced the industry to produce oils of this type which ,are low in mercaptan odor, i. e., very low in mercaptan number or even sweet to the Doctor Test. Furthermore, consumer demand has forced the industry 'to produce oils that are of relatively low aromatic hydrocarbon content. At this time the industry is making a greater .eflort to produce oils of relatively low total sulfur content, i. e., oils containing on the order of 0.25 weight percent sulfur.

Many processes are known for sweetening sour, i. e., mercaptan containing distillates boiling in the naphtha range. The better known processes are the doctor process and the copper chloride process. Because .of its simplicity and because it .does not increase the sulfur content of the naphtha, the copper chloride process is the most popular sweetening process for naphthas. The chief disability of the copper chloride process is that the color of the sweet naphtha deteriorates in storage. However, this difiiculty is readily overcome by the addition of a metal deactivator to the sweet naphtha. Numerious metal deactivators are known in this art.

It has been found that copper chloride sweetening cannot be utilized for all distillates boiling in the heavierthan-gasoline range. The process works more or less satisfactorily on 'distillates which are relatively low in sulfur content, i. e., less than about 0.25%. .Evenron some low sulfur distillates the copper chloride process cannot be used. The difiiculty with the use of the copper chloride process for sweetening sour 'distillates boiling ,in the heavier-than-gascline range is the very poor color stability of the sweet oil in storage. At this time anacceptable commercial oil must have a color of about Saybolt. For some oils the color stability problem is curable .by the use of metal decativators. However, for oils having a sulfur content on the orderof 0:5 and"higher, even 2,727,851 Patented Dec. 20, 1955 2 massive amounts of metal deactivator added to the sweet oil will not give satisfactory color stability. Further, it has been noted that the difliculty increases with increase in the maximum boiling point of the distillate being treated.

The doctor process has been used successfully to sweeten these heavy distillates and is being used commercially in spite of the increase in sulfur content of the product oil. The doctor process for this use has a disability in that the burning quality, as measured by deposits formed in domestic oil burners, is adversely affected.

For many years the burning quality of kerosenes has been improved by an extraction treatment with liquid S02 in the Edeleaneu process. This treatment removes appreciable amounts of aromatic hydrocarbons and organic sulfur compounds from the raw distillate. The treatment of furnace oils and heater oils with liquid S02 definitely improves the burning quality thereof, as measured by the deposits in domestic oil burners. However, the S02 treatment of a sour distillate does not produce a sweet product even though the mercaptan number is usually decreased by the S02 treatment.

It is an object of this invention to produce a sweet, color stable oil which boils in the heavier-than-gasoline range. Another object is to produce an oil boiling in the heavier-than-gasoline range which is substantially mercaptan-free, of good storage, color stability, and of good burning quality. A particular object is to produce a sweet, color stable oil suitable for use as burning oil, diesel fuel, and jet fuel by a treatment which involves the use of copper chloride sweetening. Another object is to treat a heavy distillate which contains sulfur in amounts in excess of about 0.25 weight percent, is sour to the Doctor Test, and contains objectionable amounts of aromatic hydrocarbons in a combination process involving the use of liquid S02 and copper chloride sweetening to produce a sweet, color stable oil of good burning quality.

The above objects and other objects notset outare attained by treating a heavy distillate, .which contains more than about 0.04 volume percentof phenols with an effective amount of liquid S02 at a temperature below about +35 R, separating an extractnphase .from arafiinate phase, eliminating S02 from :the r affinate phase to obtain a sour rafiinate oil, contacting said sour oil at a temperature below about F., in the presenceof free-oxygen, with ,a catalyst mass for a time sufiicient to sweeten said sour oil, and separating a substantially sweet oil from said catalyst mass and wherein said catalyst .mass comprises .cupric chloride, water, and an inert carrier therefor.

The feed stock to the processof this invention is a sour, i. e. mercaptan-containing, hydrocarbon ,oil which has an ASTM distillation within the range of between about 300 and .650 F. lnthe case of disitillatesderived from petroleum sources this boiling range encornpasses the so-called heavier-.than gasoline boiling range distil- ,lates. Hereafter in .this specification and in the claims materials boiling within the above range will be referred to as heavy .distillates. The feed ;to .th is process-may be straight run (virgin) distillates, .or they may .be .de-

rived from .various petroleum ;conyersion..processes,..such

as, thermal cracking, catalytic crackingQhydrodesulfurization, etc. This processis particularly suitable for virgin distillates, such as, kerosenes, heater ,oils, diesel fuels, and jet fuels.

'While the combination process of ,this invention is operable on any heavy distillates, it is particularly useful on those distillates containing objectionableamounts of aromatic hydrocarbonsandobjectionable amounts of organic sulfur'compounds. Ingeneralburningoils which contain on-the order of 5 volume percent or less -o f aromatic hydrocarbons aresuitable for use in lamps-and domestic 3 heating installations. Although sulfur content is not definitely known to be bad, in general, it is desirable to maintain the sulfur content below about 0.5 weight percent and preferably lower.

It has been discovered that the chief cause of the color instability of copper chloride sweetening oils is the presence of phenols in the raw oil. It is believed that the phenols react with the copper chloride to produce oil soluble copper phenolate complexes. It is believed these complexes are reactive and catalyze the color degradation of the oil. It has been found that the heavy distillate which contains more than about 0.04 volume percent of phenols cannot be successfully treated with copper chloride to produce a sweet, color stable oil. It has further been discovered that the phenols present in heavy distillates are. removed by treatment of said distillates with liquid S02. The SOz-free raflinate oil is readily sweetened by the copper chloride process to produce an oil which is very color stable in storage. Surprisingly enough, it has been found that a color stable oil cannot be produced by S02 treatment of a raw oil which has been sweetened by the copper chloride process prior to S02 treatment. Apparently the postulated copper phenolates are not particularly soluble in liquid S02.

It has been noted that the phenol content of an oil and the sulfur content thereof are more or less directly related. By this it is meant that for most petroleum distillates, particularly virgin distillates, the higher the sulfur content of the raw oil the higher the phenol content. For example, a heater oil derived from Mid-Continent crude contained about 0.3% of sulfur and 0.05% of phenols, whereas a heater oil of the same boiling range derived from a West Texas crude contained about 0.7% sulfur and about 0.25% phenols. In general a straight run distillate which contains more than about 0.25 weight percent of sulfur will contain an amount of phenols such that the distillate cannot be successfully copper chloride sweetened to produce a color stable oil.

The term phenols as used in this specification and in the claims is intended to include all compounds which contain the phenol group as well as phenol itself. Thus it is known that phenol, xylenol, and many other alkylated phenols are present in heavy distillates. In general the phenol content of cracked distillates is greater than that of virgin distillates.

able by using at least enough liquid S02 to exceed the solubility of S02 in the oil so that two phases are present in the extractor, i. e., a rafiinate phase containing some dissolved and occluded S02, and an extract phase consisting principally of liquid S02 and dissolved hydrocarbons and organic sulfur compounds. Usually between about 25 and 200 volume percent based on feed of liquid S02 are used in the process. It is prefered to use between about 50 and 100% of liquid S02. For optimum burning quality and color stability it is preferred to carry out the extraction at a temperature between about and F., although temperatures as low as -40? F. may be used. The temperature of treatment may be in part determined by the freezing point of the feed stock being processed.

The sour rafiinate oil from the liquid S02 treatment is sweetened by contacting said sour oil in the presence of free-oxygen with a catalyst mass. This catalyst mass comprises essentially an inert carrier, cupric chloride, and water. The catalyst may be made by using anhydrous cupric chloride or cupric chloride hydrate. Also, the cupric chloride may be derived from the reaction, in situ, product of copper sulfate, and sodium chloride or ammonium chloride.

The inert carrier may be any oil-insoluble and waterinsoluble solid material which provides an adequate surface area for the cupric chloride and water. Examples of suitable carriers are fullers earth, silica gel, diatomaceous earth, pumice, charcoal, coke, alumina, etc.

The catalyst mass used herein is in general the same as that used in the conventional copper chloride sweetening processes such as the Perco process and the Linde process. The catalyst mass should contain between about 10 and 25 weight percent of cupric chloride, between about 5 and 25 weight percent of water, and the remainder the carrier. The water content of the catalyst mass includes water adsorbed on the carrier as well as water of hydration of the cupric chloride or copper sulfate and ammonium chloride if these materials are used to provide the cupric chloride. It has been found that a better initial color of the sweet oil is obtained and markedly better color stability is attained when the temperature of the sweetening process is maintained below about +120 5., and preferably the temperature of sweetening is maintained between about and F.

It has been discovered that an oil of very much improved color stability is obtained when the temperature of contacting is maintained between about 80 and 100 F. and the water content of the catalyst mass is maintained between about 8 and 15%.

In general the amount of catalyst used to obtain a sweet oil will vary with the mercaptan number of the oil and also the contacting time. Normally between about 1 and 25 volumes of catalyst are used per 100 volumes of sour oil. The contacting time should be maintained as short as possible as prolonged contact of the oil and the catalyst has a marked adverse elfect on the color of the sweet oil.

It has been found that better results are obtained when the sour oil is contacted with the catalyst in the presence of free-oxygen or a free-oxygen containing gas such as air. Each 0.01% of mercaptan sulfur requires about 0.10 cu. ft. of oxygen per barrel of sour oil. The amount of free-oxygen needed is readily determined by one skilled in the art.

The annexed drawing which forms a part of this specification shows in schematic form one embodiment of this process.

In the drawing the sour heavy distillate from source 11 is passed through line 12 into a deaeration unit 13. The feed stock in this illustration is a virgin heater oil derived from the distillation of West Texas crude, which oil has a sulfur content of about 0.7, a phenol content of 0.2, and an A. S. T. M. boiling range between about 330 and 550 F. I

Deaeration unit 13 may comprise conventional equipment such as the vacuum deareation equipment ordinarily employed in commercial processes of liquid SOz refining of hydrocarbon oils. The deaerated feed is passed from deaerator 13 through line 14 into drying zone 16. Water is harmful to the extraction process and it is preferred that the feed oil be substantially dehydrated. Drying zone 16 may comprise conventional equipment and drying reagents, e. g., drier 16 may be a vessel packed with calcium chloride, rock salt, magnesium silicate, alumina gel, etc. In some instance it may be desired to dehydrate by means of vacuum distillation. It is to be understood that the specific form of deaerator 13 and drier 16 is no part of the present invention and that any treatment may be used which substantially elminates air and water from the feed.

The oil from drier 16 is passed through line 17 and through heat exchanger 18 where the temperature of the oil is lowered to the desired operating temperature, herein -10 F. The cold oil is passed through line 19 into a lower portion of extractor 21.

Extractor 21 is a tower packed with suitable materials in order to increase the efficiency of contacting of the feed and the liquid S02. For example, extractor 21 may be packed with Berl saddles, glass, or metal spheres, alumina balls, jack chain, etc. Also, extractor 21 may be in the form of a bubble tower which has been arranged for extraction purposes. Extractor 21 may also be provided with mechanical agitators arranged along the height of the column to improve agitation.

Extractor 21 may also be provided with heat exchangers to permit control of the temperature of contacting or to permit operation with a temperature gradient within the tower.

Although a continuous countercurrent type of extraction tower is shown in this embodiment other forms of contacting may be used, c. g., several batch countercurrent extraction zones may be used, or even several independent extraction stages may be used.

Liquid S02 from source 22 is passed through line 23 into an upper portion of extractor 21. The extraction must be carried out under liquid conditions and sufilcient pressure must be applied to extractor 21 in order to maintain the S02 in the liquid phase. In this illustration the total amount of liquid S02 used is 75 volumes per 100 volumes of feed oil. The contacting time in extractor 21 is such that the aromatic hydrocarbon content is reduced to about 5 volume percent and substantially all the phenols are removed. A suitable time is about minutes.

From the bottom of extractor 21 an extract phase is removed and is passed through line 26 into stripper 27 which is equipped with a reboiler 28. in stripper 27 the S02 is removed from the extract and is taken overhead through line 29. A substantially SOz-free extract is removed from stripper 27 through line 31 and is sent to storage not shown.

The ratrlnate phase is removed from extractor 21 through line 33 and is passed into stripper 34 which is provided with reboiler 36. In stripper 34 the S02 is removed overhead by way of line 37 and is passed into line 29.

In the course of operation some impurities such as water and H28 pass into the S02 and these should be re moved before the S02 is recycled to the process. The contaminated S02 in line 29 is passed into purification zone 38 where the impurities are removed. The purified S02 is passed through line 39 into line 23 and is reused in extractor 21. Purification zone 38 is shown schematically and may be any conventional equipment such as is used in liquid S02 refining of hydrocarbon oils.

The substantially SOz-free raiiinate oil is removed from stripper 34 by way of line 41 and a dilute aqueous caustic solution, e. g., 10% NaOH, is passed from source 42 through line 43 into line 41. The mixture in line 41 is passed into mixer 44 wherein the oil and aqueous caustic are thoroughly intermingled in order to neutralize the S02 remaining in said oil.

The mixture from mixer 44 is passed through line 46 into settler 47 where two phases separate. A spent caustic phase is removed from a lower portion of settler 47 by way of line 48 and is sent to caustic disposal not shown. The neutralized rafi'inate oil is withdrawn from settler 47 by way of line 49 and is passed into salt drum 51.

The remaining traces of aqueous caustic are removed from the oil in salt drum 51. Salt drum 51 may be any vertical vessel provided with a bed of coarse rock salt. instead of a salt drum an efiicient coalescer provided with excelsior, fiber glass, steel wool, etc. may be used to remove the aqueous caustic from the oil. Brine is periodically removed from the bottom of salt drum 51 by way of valved line 52.

The oil from salt drum 51 is passed into line 53. Commercial oxygen from a source 56 is passed through line 57 into line 53 where it meets the sour oil. Air can be utilized in the process instead of commercial oxygen. No attempt is made herein to depict the equipment used for injecting commercial oxygen as many methods of doing this are known to the art. The oxygen-sour oil stream is passed from line 53 into mixer 58 which is provided 6 with heat exchanger 59 wherein they are thoroughly intermingled before passing into line 60.

A small amount of sour oil may be withdrawn from line 53 by way of valved line 61 and passed into agitated vessel 62. Catalyst mass from source 63 is passed by way of line 64 into vessel 62. In this embodiment the catalyst mass comprises about 12% water, about 20% cupric chloride, and the remainder finely powdered Attapulgus clay. The catalyst mass herein is dry in appearance and flows freely, much like dry sand. As is necessary, makeup catalyst-sour oil slurry from vessel 62 is passed through valved line 66 into line 60.

The mixture of makeup catalyst and sour oil is passed from line 6%) into eductor 67. The eductor 67 causes the catalyst oil slurry to flow through line 68 into reactor 69.

Reactor 69 is a cone-bottomed vessel. The catalyst settles out of the oil into the bottom of reactor 69. Reactor 69 is of such a size that a sufficient contacting time is attained to produce a substantially sweet efiluent oil. The temperature in reactor 69 is maintained in this embodiment at F. A slurry of catalyst and oil is withdrawn from the bottom of reactor 69 and is passed through line 71 and valved line 72 into eductor 67 for recycle to the sweetening step. Periodically spent catalyst may be withdrawn from the system by way of line 71 and valved line 73.

The effluent oil from reactor 69 contains some suspended catalyst, which catalyst must be removed in order to improve the appearance of the oil and prevent color degradation. The efiluent oil is withdrawn from reactor 69 by way of line 76. In order to remove the suspended catalyst, wash water from source 77 is passed through line 78 into line 76. The oil-water stream from line 76 is thoroughly intermingled in mixer 79 before being passed by way of line 81 into settler 82.

A lower water layer is withdrawn from settler 82 and sent to disposal by way of line 83. The oil layer in settler 32 is withdrawn by way of line 34 and passed through salt drum 86. Salt drum 86 is similar to salt drum S1 and serves the purpose of substantially dehydrating the wet oil. Brine is periodically removed from salt drum 36 by way of valved line 37. A sweet product oil is removed by way of line 88.

Under some conditions of operation the product oil from line 33 will have a satisfactory color stability. Normally feed color stability can be attained only by adding some metal deactivator to the sweet oil. Any one of the many metal deactivators known in the art may be used. in this embodiment 2 lbs/1000 bbls. of sweet oil of N,Ndisalicylidine-1,2-diaminopropane are added to the oil.

The embodiment of this process shown in the drawing and described above illustrates what is commonly known as the slurry method of copper chloride sweetening. Other methods of copper chloride sweetening can be used, c. g., instead of using a finely divided free-flowing catalyst mass, catalyst particles may be larger and placed in a fixed position in a reactor. The sour oil and freeoxygen then may be passed through the bed of catalyst at a space velocity such that substantially sweet oil will emerge from the catalyst bed. Still other methods of contacting the catalyst and the sour oil may be readily devised.

The illustration described above is necessarily generalized and many items of process equipment such as pumps, valves, etc. have been omitted to simplify the drawing and the description. The addition of miscellaneous items of equipment is a matter of technical skill such as is present among those skilled in this art.

The results obtainable by the process of this invention are illustrated herein. The feed to the illustrative test was a West Texas virgin heater oil of mediocre burning quality and of exceptionally poor color stability when copper chloride sweetened. The physical characteristics of the heater oil are set out below:

API gravity 40.3

The color stability on storage of a sweet oil was determined by means of a laboratory test. The results of this laboratory test are known as aged color. In this test 100 ml. of the oil are maintained in an open beaker for 20 hours at 200 F. At the end of this time the 'Saybolt color of the oil is determined. It has been found that an aged color of +10 Saybolt or better indicates that the oil will have a satisfactory color stability in commercial storage.

Test 1 In this test a sample of raw oil described above was sweetened using a bench scale continuous pilot plant. This pilot plant closely simulates results on a commercial unit. In this test the catalyst mass consisted of 13 Weight percent water, 20 weight percent cupric chloride, and 67 Weight percent of Attapulgus clay fines. Seventeen ml. of catalyst was used per 100 ml. of sour distillate. The sour distillate was saturated with air and this air containing distillate was contacted with the catalyst at a temperature of 91 F. for 2 minutes. The catalyst was filtered from the sweet oil. The suspended catalyst was removed by water washing the oil at a temperature of 120 F. and the sweet oil was freed of occluded water by passage through a bed of glass wool. The sweet oil was inhibited with 0.001% of N,N'disalicylidine-l,2-diaminopropane. This amount corresponds to 2 lbs. of deactivator per 1000 bbls. of oil.

The oil from this treatment was sweet to the Doctor Test and had a color of +9 Saybolt. The aged color of the inhibited oil was 5 NPA.

It has been found that improved color stability can be obtained for oils of high phenol content by water washing the catalyst containing sweet oil at a temperature between about 110 and 150 F. Satisfactory aged color can usually be obtained by water washing at ambient temperatures.

Test 2 In this test West Texas distillate was copper chloride sweetened and then the burning quality of the sweet oil was improved by liquid S02 treatment. The sweet uninhibited oil produced in Test 1 was contacted at 4 F. with 50 volume percent, based on charge of liquid S02. The raffinate phase was separated from the extract phase. The rafiinate phase was contacted with 50 volume percent of liquid S02, based on fresh charge and a second raflinate phase separated from a second extract phase. The second raffinate phase was contacted with 50 volume percent of liquid S02, based on fresh charge and a third rafiinate phase separated from a third extract phase. The third rafiinate phase was stripped of S by general heating on a water bath. The last traces of S02 were removed from the oil by washing with a 10% aqueous caustic solution. The neutral oil was passed through a glass wool coalescer to remove residual aqueous caustic solution.

The sweet product oil was inhibited with 0.001% of metal deaetivator. The color of the product oil was 0 Saybolt and the aged color was 1 NPA.

Analysis of the sweet oil produced in this test showed about 5 volume per cent of aromatic hydrocarbons to be present. This oil had only a moderate improvement in burning quality as measured by a laboratory deposit test.

Test 3 In this test the sour distillate was first treated with liquid S02 before being sweetened'with copper chloride catalyst. The treatment was carried out at -4 F. in three batch stages as described in Test 2. It has been found that this method of S02 treatment is closely equivalent to a continuous countercurrent treatment when using half as much liquid S02 as was used in toto in the batch extraction. Thus in a countercurrent system, 75 volume percent of liquid S02 would be used, based on sour distillate charged.

The raflinate phase was stripped of S02 on awater bath. Residual S02 was removed by washing with a 10% aqueous caustic solution. The sour oil was passed through a glass wool coalescer to remove entrained caustic solution. The results of this S02 extraction are given below:

Raflinate:

Yield, volume per cent 81.3 Aromatic content, volume per cent 6.5 Mercaptan number 35 Sulfur, weight per cent 0.21 Initial color +30 Aged color +28 Extract:

Yield, volume per cent 19.7 Sulfur, weight per cent 2.86

The sour, SO2-free rafiinate oil was then copper chloride sweetened by the same method described in Test 1. The sweet oil was inhibited with 0.001% of metal deactivator. The initial color of the inhibited oil was +30 Saybolt and the aged color thereof was +28 Saybolt. The aged color of this oil without inhibitor was +14 Saybolt.

This oil had a superior burning rating and was much better in the laboratory deposit test than a standard sweet test oil derived from Mid-Continent crude. The standard oil before sweetening has a mercaptan number of 8, a total sulfur content of 0.3%, a phenol content of 0.05 and an aromatic content of about 5%. The standard sweet oil is obtained by copper chloride sweetening the sour oil according to the method of Test 1.

Test 4 In this test a sample of West Texas sour distillate was treated in exactly the same manner as in Test 3 except that the water washing step following the separation of the catalyst from the substantially sweet oil was carried out at F. This oil when inhibited with the same amount of metal deactivator as used in Test 3 gave an aged color of +16 Saybolt.

It is apparent from the tests presented above that the process of this invention produces a sweet oil having an astonishingly good storage, color stability, and excellent burning quality.

Thus having described the invention, what is claimed 1. A process for refining a sour distillate that boils within the range of about 300 to 650 F. and that contains at least 0.25 weight percent of total sulfur and at least 0.05 volume percent of phenols, which process comprises (1) contacting said sour distillate with between about 25 and 200 volume percent of liquid S02 at a temperature between about +35 and 40 F., (2) separating an extract phase from a raflinate phase, (3) treating said raffinate phase to produce a substantially SO2- free raffinate oil, (4) contacting said raflinate oil in the presence of free-oxygen at a temperature between about 80 and about F. for a time sufficient to produce a sweet rafiinate oil with a catalyst mass consisting of between about 5 and 25 weight percent of cupric chloride and water, respectively, and the remainder an inert carrier, and separating a sweet oil from said catalyst.

2. The process of claim 1 wherein an efiective amount of a copper metal deactivator is added to the sweet oil of step 5.

3. The process of claim 1 wherein the amount of liquid S02 used in step 1 is between about 50 and 100 volume percent and the temperature of contacting is between about and F.

4. The process of claim 3 wherein the temperature of contacting in step 4 is between about 80 and 100 F. and the catalyst mass contains between about 8 and 15 weight percent of water.

5. A process for producing a sweet, color stable oil of good burning quality, which process comprises contacting a sour petroleum distillate boiling between about 325 and 550 F. that contains about 0.7 weight percent of sulfur and about 0.2 volume percent of phenol with between about and 100 volume percent, based on said distillate, of liquid S02 at a temperature between about +10 and 20 F., separating a raifinate phase from an extract phase, treating said rafiinate phase to produce a substantially SOz-free rafiinate oil, contacting said raftinate oil at a temperature between about and F., in the presence of free-oxygen, with a catalyst mass consisting of between about 8 and 15 weight percent of water, between about 5 and 25 weight percent of cupric chloride, and the remainder an inert carrier, for a time sufiicient to substantially sweeten said rafiinate oil, separating a substantially sweet rafi'inate oil from said catalyst mass, Water washing said sweet oil at a temperature of at least about R, separating said washed oil from a lower Water layer, and adding to said washed oil an effective amount of N,Ndisalicylidine-1,2-diaminopropane.

References Cited in the file of this patent UNITED STATES PATENTS 1,810,369 Peterkin June 16, 1931 2,042,052 Hoover May 26, 1936 2,094,485 Buell Sept. 28, 1937 

1. A PROCESS FOR REFINING A SOUT DISTLLATE THAT BOILS WITHIN THE RANGE OF ABOUT 300* TO 650* F. AND THAT CONTAINS AT LEAST 0.25 WEIGHT PERCENT OF TOTAL SULFUR AND AT LEAST 0.05 VOLUME PERCENT OF PHENOLS, WHICH PROCESS COMPRISES (1) CONTACTING SAID SOUR DISTILLATE WITH BETWEEN ABOUT 25 AND 200 VOLUME PERCENT OF LIQUID SO2 AT A TEMPERATURE BETWEEN ABOUT +35* AND -40* F., (2) SEPARATING AN EXTRACT PHASE FROM A RAFFINATE PHASE, (3) TREATING SAID RAFFINATE PHASE TO PRODUCE A SUBSTANTIALLY SO2FREE RAFINATE OIL, (4) CONTACTING SAID RAFFINATE OIL IN THE PRESENCE OF FREE-OXYGEN AT A TEMPERATURE BETWEEN ABOUT 80* AND 120* F. FOR A TIME SUFFICIENT TO PRODUCE A SWEET RAFFINATE OIL WITH A CATALYST MASS CONSISTING OF BETWEEN ABOUT 5 AND 25 WEIGHT PERCENT OF CUPIC CHLORIDE AND WATER, RESPECTIVELY, AND THE REMAINDER AN INERT CARRIER, AND (5) SEPARATING A SWEET OIL FROM SAID CATALYST. 